1. Field of the Invention
The present invention relates to an endoscope apparatus which is inserted into the body of a subject mainly for conducting an endoscopic surgery.
2. Description of the Related Art
An endoscope apparatus such as an electronic endoscope takes an image of a body to be observed which is illuminated by illumination light by using a CCD (charge coupled device), namely, a solid imaging device and gives a predetermined signal processing to the imaged observation image, thereby displaying the image on monitors. An endoscope apparatus is, therefore, provided with a scope loading a CCD and having an insertion portion, a processor unit having a light source for supplying illumination light, which gives a predetermined signal processing to an observation image taken by the CCD, and monitors for displaying the observation image which was subjected to signal processing in the processor unit. This type of endoscope apparatus can be used for not only in making a diagnosis or observation but also used in endoscopic surgery such as a cholecystectomy by an abdominoscope. An operator can carry out a procedure for an affected part by using treatment equipment such as forceps and scalpels while observing observation images displayed on monitors.
The above-described CCD takes a whole image of a wide area to the greatest possible extent so that an operator can recognize both the position of an affected part and that of treatment equipment. As described in JP-A-2001-340292, where an image of the vicinity of the affected part (interest area) is enlarged and displayed, the treatment equipment displayed on a whole image displaying the affected part and the treatment equipment may disappear from the screen. Therefore, the treatment equipment is not appropriately operated, thus, resulting in loss of a smooth and reliable operation of the equipment.
Under these circumstances, it has been demanded that a whole image and an enlarged image of an interest area be displayed at the same time. In response to such a demand, for example, JP-A-1-99083 has disclosed a system by which a whole image and an enlarged image are displayed on the screen of one monitor. More specifically, the screen of the monitor is divided to display a whole image and an enlarged image of an interest area.
In the above-described invention of JP-A-1-99083, a whole image and enlarged image of the interest area are displayed on the same monitor, which makes narrower the effective area for displaying the respective images, therefore, a problem is brought about that it is difficult of recognize the images.
Further, an enlarged image of an interest area is generated by electronically enlarging a whole image. The fact has been widely known that, in general, when an image is electronically enlarged, one pixel constituting an original image is given a certain processing (for example, interpolation) and displayed in a plurality of pixels, causing jaggy (zigzag) on a curved line or a diagonal line. Therefore, the contour of the image may be blurred to such an extent that an affected part cannot be accurately visualized for the details, depending on an enlargement ratio. In order to obtain a clear image of the interest area, it is preferable that no electronic enlargement processing is given at all or an enlargement ratio is kept to the lowest possible extent, thereby displaying an image on a monitor in such a way that processing given to respective pixels constituting the image taken by a CCD is suppressed as much as possible.